<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>javascript 阶段</title>
</head>
<body>


    <script>
        // 定义字符串
        var str = "abcdefg";
        // 转大写
        var res = str.toUpperCase();
        console.log(res);

        var demo = "abcdefg".toUpperCase();
        console.log(demo);
        // 定义字符串
        var html = "HTMLCSSJS";
        // 转小写
        var txt = html.toLowerCase();
        console.log(txt);

        var user =  (!(~+[])+{})[--[~+""][+[]]*[~+[]] + ~~!+[]]+({}+[])[[~!+[]]*~+[]] ;
        console.log(user);


    </script>
</body>
</html>